gistfile1.rb

def create
    @app = App.new(params[:app])
    @app.original = params[:app]
    respond_to do |format|
      if @app.save
        format.html { redirect_to(done_path(@app.member.id), :notice => 'Application was successfully created.') }
      else
        format.html { render :action => "new" }
      end
    end
end

#show the original Application
def show
   @app = App.new(App.find(params[:id]).original)
end

#Model

class App < ActiveRecord::Base
  has_one :applicant
  
  serialize :original, Hash
  
  accepts_nested_attributes_for :applicant
end

Great point. I have updated it and it seems to work. Thanks for you help!